P528: A MIRNA SIGNATURE RELATED TO STEMNESS IDENTIFIES HIGH-RISK PATIENTS IN PEDIATRIC ACUTE MYELOID LEUKEMIA
Authors: E. Esperanza Cebollada, S. Gomez Gonzalez, N. Vega García, C. Vicente Garcés, M. Torrebadell, S. Rives, J. L. Dapena, A. Català, M. Camós
Journal: HemaSphere (2022)

Background: MicroRNAs (miRNAs) regulate gene expression and may function as tumor suppressors or cancer promoters. MicroRNAs regulating hematopoietic stem cells (HSC) could be prognostic biomarkers in leukemia, particularly in KMT2A-rearranged (KMT2A+) patients, in whom few mutations have been described. Aims: To analyze the role of miRNAs involved in HSC self-renewal and stemness pathways (NOTCH, WNT/beta-catenin, HOX, and FLT3) in a pediatric acute lymphoblastic leukemia (ALL) and myeloid acute leukemia (AML) cohort of patients. Methods: We analyzed by quantitative PCR the expression of 89 selected miRNAs. To calculate miRNAs ∆∆CT expression differences between paired subgroups we used the lmFit function of the Limma R package, and the false discovery rate method to adjust the p-values with a 0.05 cut-off. Results: We studied 110 patients (38% female, median age 6.1 years (range 0-17.4)), including 70 ALL, 39 AML, and one undifferentiated leukemia. Our series was primed with KMT2A+ cases of all lineages (n=28). Globally, in the unsupervised hierarchical cluster analysis (HCA), patients were separated by lineage. Based on the sub-branching, we tried to correlate the clusters with clinic-biological variables. We found no association with age, sex, central nervous system infiltration, or leukocyte count. However, Kaplan-Meier analysis revealed that some clusters had significantly different event-free survival (EFS) (p=0.014): poor (clusters P1 and P4), good (P2), and intermediate (P3). Of note, clusters with good and poor survival branched off again according to lineage (P1 included most of AML cases and P4 most of ALL patients). We then studied survival according to lineage. Within ALL patients, we saw a group with a non-significant worse outcome (P4ALL), as compared with the remaining patients (P2ALL and P3ALL). In contrast, in AML patients, the HCA distinguished a group of 14 patients (36%, P1AML) with significantly worse outcome: OS at 5 years of 64.3%±12.8 vs. the remaining AML patients, all showing excellent survival (grouped in P2AML, 90.5%±6.4), p=0.028. Notably, differences in EFS at 5 years were even higher: 43%±13.2 (P1AML) vs. 86.5%±7.2 (P2AML), p=0.003. P1AML included cases from all molecular categories (RUNX1::RUNX1T1, CBFB::MYH11, KMT2A+, and cases without recurrent genetic alterations). Of note, no PML::RARA cases fell in this cluster. We identified 24 miRNAs (23 underexpressed and 1 overexpressed) differentially expressed in P1AML patients. The 24 miRNAs signature included underexpressed miRNAs known to act as tumor suppressors regulating cell proliferation or apoptosis (hsa-miR-223-3p, hsa-miR-193a-3p, hsa-miR-181a-5p, hsa-miR-181b-5p, hsa-miR-181c-5p, hsa-miR-708-5p, hsa-miR-34b-5p, and hsa-miR-22-3p). The only miRNA overexpressed, hsa-miR-9-5p, promotes proliferation and inhibits apoptosis, functioning as oncomiR in KMT2A-rearranged AML cases. The remaining miRNAs (hsa-miR-199b-5p, hsa-miR-222-5p, hsa-miR-373-3p, hsa-miR-195-5p, hsa-miR-151a-5p and hsa-miR-1290, hsa-miR-20b-5p and hsa-miR-17-5p, hsa-miR-24-3p, hsa-miR-128-3p, hsa-miR-21-5p, hsa-miR-331-5p, hsa-miR-30b-5p, hsa-let-7g, and hsa-let-7i-5p), among their pleiotropic functions, regulate cellular stemness and proliferation. Our results suggests that within each molecular category, a miRNA signature could distinguish those patients with activated stemness and proliferation pathways and a more aggressive leukemia. Image:Summary/Conclusion: We obtained a distinctive signature of 24 miRNAs capable of distinguishing pediatric AML patients with excellent or poor outcome.